The attained flexibility of tree constraints is inherently accompanied by the presence of degenerate scenarios due to the soft assignment operation. In particular, similarly to softmax-based pooling, we have to deal with two degenerate behaviours: i) all node clusters reflect the same tree structure; ii) nodes are assigned to a single node cluster while the remaining node clusters are ignored. Albeit there exist valid solutions as in [1]}, some modifications are required since softmax properties no longer hold true.
